In ECMP processes, fresh slurries/electrolytes (“slurry or slurries”) are delivered to an ECMP tool for removing metals from wafers. This metal may be, for example, copper. This removal occurs either electrochemically, i.e., the wafer is under an oxidation potential for oxidizing solid metal at the surface to metal ions, which dissolve into the slurry, or by a abrasion, i.e., the slurry scrapes off small particles of the wafer metal into the slurry. In the latter case, particles are oxidized in the slurry medium. In both scenarios, the slurry becomes contaminated by the metal ions which were on the surface of the wafer.
As is known, ECMP is a costly process in semiconductor manufacturing. Most of these costs are attributed to consumables such as polishing pads and slurries. At present time, slurries are treated as a single use item, because once the slurry is contaminated with the metal ions, they cannot be used again for polishing or other ECMP processes.
The slurries comprise abrasives to smooth the surface of the semiconductor wafer, thereby removing parts of its surface. They further comprise corrosive chemicals, buffers and colloids to maintain the mixture in dispersion. The properties of these diverse ingredients relate directly to the quality of the finished product and are qualified in measurements such as the rate of removal of surface material, uniformity of removal, planarity of the polished surface, and defects present. However, due to the metal ion contamination, the quality of the slurry is severely compromised and, as such, it is not possible to maintain the quality of the finalized product using this contaminated slurry. Accordingly, the slurry is discarded, thus, significantly adding to the costs of the ECMP processes. That is new slurry must be introduced into the system in order to maintain the required quality necessary for ECMP processing.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.